Autonomic abnormalities in cyclic vomiting syndrome

Background: Although cyclic vomiting syndrome (CVS) is associated with migraine, and migraine in turn is associated with orthostatic tachycardia, few studies have explored the association of CVS and autonomic dysfunction. We describe the results of autonomic testing in 6 children with characteristic CVS. Patients and Methods: All patients fully met the established criteria for the diagnosis of CVS, were well hydrated, and were beyond their episode of vomiting. We performed 3 tests of cardiovascular function and 1 sudomotor test, using standard previously published methods. Results: The findings were surprisingly uniform, with normal cardiovascular responses to deep breathing and to the Valsalva maneuver in all patients, a significant increase in heart rate (> 30 beats per minute) with tilt testing, and a vasodepressor tendency in 2 patients. Interestingly, abdominal pain occurred at blood pressure nadir in both these patients and in a third patient without the vasodepressor findings but who described syncope clinically. Sudomotor test results were abnormal in all 6 patients, with reduced responses in 5 of 6 and exaggerated responses in the 6th. All 6 patients reported a personal or family history of migraine headaches. Conclusions: CVS is associated with remarkably uniform primarily sympathetic autonomic dysfunction, affecting mainly the vasomotor and sudomotor systems, and compatible with an underlying autonomic neuropathy. The occurrence of symptoms during tilt testing in half the patients suggests that these findings may play a true pathophysiologic role. A vagally modulated sympathetic effect is postulated as the best mechanistic model to account for all current physiologic data on cyclic vomiting and gastroparesis.